The Fairy-Land of Science eBook

Now we come lastly to the Orchis flower. Mr.
Darwin has written a whole book on the many curious
and wonderful ways in which orchids tempt bees and
other insects to fertilize them. We can only
take the simplest, but I think you will say that even
this blossom is more like a conjuror’s box than
you would have supposed it possible that a flower
could be.

Let us examine it closely. It has sic deep-red
covering leaves, Fig. 62, three belonging to the calyx
or outer cup, and three belonging to the corolla or
crown of the flower; but all six are coloured alike,
except that the large on in front, called the “lip”,
has spots and lines upon it which will suggest to you
at once that they point to the honey.

But where are the anthers, and where is the stigma?
Look just under the arch made by those three bending
flower-leaves, and there you will see two small slits,
and in these some little club-shaped bodies, which
you can pick out with the point of a needle.
One of these enlarged is shown. It is composed
of sticky grains of pollen held together by fine threads
on the top of a thin stalk; and at the bottom of the
stalk there is a little round body. This is
all that you will find to represent the stamens of
the flower. When these masses of pollen, or pollinia
as they are called, are within the flower, the knob
at the bottom is covered by a little lid, shutting
them in like the lid of a box, and just below this
lid you will see two yellowish lumps, which are very
sticky. These are the top of the stigma, and
they are just above the seed-vessel, which you can
see in the lowest flower in the picture.

Now let us see how this flower gives up its pollen.
When a bee comes to look for honey in the orchis,
she alights on the lip, and guided by the lines makes
straight for the opening just in front of the stigmas.
Putting her head into this opening she pushes down
into the spur, where by biting the inside skin she
gets some juicy sap. Notice that she has to bite,
which takes time.

You will see at once that she must touch the stigmas
in going in, and so give them any pollen she has on
her head. but she also touches the little lid and
it flies instantly open, bringing the glands at the
end of the pollen-masses against her head. These
glands are moist and sticky, and while she is gnawing
the inside of the spur they dry a little and cling
to her head and she brings them out with her.
Darwin once caught a bee with as many as sixteen
of these pollen-masses clinging to her head.

But if the bee went into the next flower with these
pollinia sticking upright, she would simply put them
into the same slits in the next flower, she would
not touch them against the stigma. Nature, however,
has provided against this. As the bee flies
along, the glands sticking to its head dry more and
more, and as they dry they curl up and drag the pollen-masses
down, so that instead of standing upright, as in 1,
Fig. 63, they point forwards, as in 2.